Toughened Cyanoacrylate Compositions

Abstract

Curable cyanoacrylate compositions are reported that comprise cyanoacrylate and a thermoplastic polyurethane (TPU) components. Such compositions are toughened cyanoacrylate compositions exhibiting long term viscosity stability when stored for prolonged periods at room temperature (25 C.). TPU components are reported having structural units in which at least one of the structural units has the formula OR.sup.1OArOR.sup.2O, wherein Ar is a C.sub.6-C.sub.20 aromatic group with at least one aromatic ring; R.sup.1 is a C.sub.2-C.sub.10 alkyl group; and R.sup.2 is a C.sub.2-C.sub.10 alkyl group. The thermoplastic polyurethane (TPU) component may be present in the curable cyanoacrylate composition from about 1 wt % to about 40 wt %, for example from about 2 wt % to about 30 wt %, such from about 3 wt % to about 20 wt %, suitably from about 5 wt % to about 10 wt %, based on the total weight of the composition.

Claims

1. A curable cyanoacrylate composition comprising: (i) a cyanoacrylate; and (ii) a thermoplastic polyurethane (TPU) having a chain formed from structural units; wherein at least one of the structural units of the chain of the thermoplastic polyurethane (ii) has the formula:
OR.sup.1OArOR.sup.2O, wherein: Ar is a C.sub.6-C.sub.20 aromatic group with at least one aromatic ring; R.sup.1 is a C.sub.2-C.sub.10 alkyl group; and R.sup.2 is a C.sub.2-C.sub.10 alkyl group, and wherein the thermoplastic polyurethane (TPU) (ii) is present in the curable cyanoacrylate composition from about 1 wt % to about 40 wt %, for example from about 2 wt % to about 30 wt %, such from about 3 wt % to about 20 wt %, suitably from about 5 wt % to about 10 wt %, based on the total weight of the composition.

2. A curable cyanoacrylate composition as claimed in claim 1 wherein the aromatic group Ar in the structural unit with the formula:
OR.sup.1OArOR.sup.2O is selected from: benzene, methyl benzene, dimethylbenzene, ethylbenzene, trimethylbenzene, tetramethylbenzene, diethylbenzene, triethylbenzene, naphthalene, methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene, tetraethylbenzene, tetramethylnaphthalene, pentamethylnaphtalene, hexamethylnaphthalene, ethylnaphthalene, diethylnaphthalene, or triethylnaphthalene.

3. A curable cyanoacrylate composition as claimed in claim 1 wherein the aromatic group Ar in the structural unit with the formula:
OR.sup.1OArOR.sup.2O is a benzene group or a naphthalene group.

4. A curable cyanoacrylate composition according to claim 1 wherein at least one of the alkyl groups R.sup.1 and R.sup.2 in the structural unit with the formula:
OR.sup.1OArOR.sup.2O is a C.sub.2 alkyl group.

5. A curable cyanoacrylate composition according to claim 1 wherein the alkyl groups R.sup.1 and R.sup.2 in the structural unit with the formula:
OR.sup.1OArOR.sup.2O are both C.sub.2 alkyl groups.

6. A curable cyanoacrylate composition as claimed in claim 1 wherein the structural unit with the formula:
OR.sup.1OArOR.sup.2O is formed from hydroquinone bis(2-hydroxyethyl) ether (HQEE).

7. A curable cyanoacrylate composition according to claim 1, wherein the structural unit with the formula:
OR.sup.1OArOR.sup.2O is present in the thermoplastic polyurethane (TPU) (ii) in an amount from about 0.5 wt % to about 50 wt %, such as from about 1 wt % to about 20 wt %, for example from about 5 wt % to about 10 wt % based on the total weight of the thermoplastic polyurethane (ii).

8. A curable cyanoacrylate composition as claimed in claim 1, wherein the thermoplastic polyurethane (TPU) (ii) is prepared using a polyol selected from the group comprising a polyester-polyol, a co-polyester-polyol, a polyether-polyol, a co-polyether-polyol, a polycaprolactone-polyol, and a co-polycaprolactone-polyol.

9. A curable cyanoacrylate composition as claimed in claim 9, wherein the polyol used in the preparation of the thermoplastic polyurethane (TPU) (ii) is a polyester-polyol or a co-polyester-polyol.

10. A curable cyanoacrylate composition as claimed in claim 10, wherein the polyol used in the preparation of the thermoplastic polyurethane (TPU) (ii) is a co-polyester formed from a dicarboxylic acid and 1,6-hexanediol.

11. A curable cyanoacrylate composition as claimed in claim 10 wherein the polyol used in the preparation of the thermoplastic polyurethane (TPU) (ii) is a linear polyester-polyol formed from a dicarboxylic acid and 1,6-hexanediol, and wherein the linear polyester-polyol has a hydroxyl number of from about 1 to about 60 mg KOH/g, for example from about 16 to about 54 mg KOH/g, such as from about 27 to 34 mg KOH/g, as measured according to ASTM E222.

12. A curable cyanoacrylate composition according to claim 1 wherein the cyanoacrylate (i) is selected from the group comprising ethyl 2-cyanoacrylate and -methoxycyanoacrylate.

13. A curable cyanoacrylate composition according to claim 1 wherein the cyanoacrylate component is present in an amount of about 50 wt % to about 99 wt % based on the total weight of the cyanoacrylate composition.

14. A curable cyanoacrylate composition according to claim 1 wherein the cyanoacrylate component is present in an amount of about 60 wt % to about 90 wt % based on the total weight of the cyanoacrylate composition.

15. A curable cyanoacrylate composition according to claim 1 wherein the thermoplastic polyurethane (TPU) (ii) is present in an amount of about 1 wt % to about 40 wt % based on the total weight of the cyanoacrylate composition.

16. A curable cyanoacrylate composition according to claim 1 wherein the thermoplastic polyurethane (TPU) (ii) is present in an amount of about 5 wt % to about 20 wt % based on the total weight of the cyanoacrylate composition.

17. A curable cyanoacrylate composition according to claim 1 further comprising a stabiliser in an amount from about 0.0005 wt % to about 5 wt % based on the total weight of the cyanoacrylate composition.

18. A curable cyanoacrylate composition according to claim 17 wherein the stabiliser is selected from BF.sub.3, SO.sub.2, or HF.

19. A curable cyanoacrylate composition according to claim 1 further comprising ultra-high molecular weight polyethylene in an amount from about 0.05 wt % to about 5 wt % based on the total weight of the cyanoacrylate composition.

20. A curable cyanoacrylate composition as claimed in claim 1 wherein the viscosity of the uncured composition as measured at 25 C. does not decrease by greater than 5% from the starting viscosity over 30 days of storage at 25 C.

21. A curable cyanoacrylate composition as claimed in claim 1, wherein the composition further comprises an antioxidant at an amount from about 0.01 wt % to about 1 wt %, such from about 0.1 wt % to about 0.8 wt % such as from about 0.2 wt % to about 0.5 wt % by weight based on the total weight of the composition.

22. A curable cyanoacrylate composition as claimed in claim 21, wherein the antioxidant is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).

23. A method of preparing a curable cyanoacrylate composition that retains a stable viscosity for at least 30 days when stored at 25 C., the viscosity measured at 25 C., wherein the method involves preparing a composition comprising from about 60 wt % to about 90 wt % of a cyanoacrylate with from about 1 wt % to about 40 wt % of a TPU, wherein the percentages are by weight based on the total weight of the composition and wherein the TPU has been prepared from: a polyol selected from the group comprising a polyester-polyol, a co-polyester-polyol, a polyether-polyol, a co-polyether-polyol, a polycaprolactone-polyol, and a co-polycaprolactone-polyol; and an isocyanate compound selected from the group comprising 1,4-diisocyanatobenzene (PPDI), toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (4,4-MDI), 2,4-diphenylmethane diisocyanate (2,4-MDI), polymethylene poly(phenyl isocyanate) (PMDI), 1,5-naphthalene diisocyanate (NDI), bitolylene diisocyanate (TODI), 1,3-xylene diisocyanate (XDI), p-1,1,4,4-tetramethylxylene diisocyanate (p-TMXI), m-1,1,3,3-tetramethylxylylene diisocyanate (m-TMXDI), 1,6-diisocyanato-2,4,4-trimethylhexane, 1,4-cyclohexane diisocyanate (CHDI), 1,4-cyclohexanebis(methylene isocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), dicyclohexylmethane diisocyanate (H12MDI), triphenylmethane-4,4,4-triisocyanate; and a chain extender with the formula:
HOR.sup.1OArOR.sup.2OH, wherein Ar is a C.sub.6-C.sub.20 aromatic group with at least one ring, R.sup.1 is a C.sub.2-C.sub.10 alkyl group, and R.sup.2 is a C.sub.2-C.sub.10 alkyl group.

24. The method according to claim 23 of preparing a curable cyanoacrylate-based composition that retains a stable viscosity for at least 30 days when stored at 25 C., the viscosity measured at 25 C., wherein the TPU has been prepared from a polyol selected from the group comprising a polyester-polyol, a co-polyester-polyol, a polyether-polyol, a co-polyether-polyol, a polycaprolactone-polyol, and a co-polycaprolactone-polyol, and an isocyanate compound selected from the group comprising 1,4-diisocyanatobenzene (PPDI), toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (4,4-MDI), 2,4-diphenylmethane diisocyanate (2,4-MDI), polymethylene poly(phenyl isocyanate) (PMDI), 1,5-naphthalene diisocyanate (NDI), bitolylene diisocyanate (TODI), 1,3-xylene diisocyanate (XDI), p-1,1,4,4-tetramethylxylene diisocyanate (p-TMXI), m-1,1,3,3-tetramethylxylylene diisocyanate (m-TMXDI), 1,6-diisocyanato-2,4,4-trimethylhexane, 1,4-cyclohexane diisocyanate (CHDI), 1,4-cyclohexanebis(methylene isocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), dicyclohexylmethane diisocyanate (H12MDI), triphenylmethane-4,4,4-triisocyanate, and a chain extender with the formula:
HOR.sup.1OArOR.sup.2OH, wherein said chain extender is hydroquinone bis(2-hydroxyethyl) ether (HQEE).

Description

DESCRIPTION OF THE DRAWINGS

[0114] FIG. 1: Bar chart showing the effect of storage temperature (25 C. and 4 C.) on the viscosity over time of an ethyl cyanoacrylate composition (Comparative Example 1; CEx1) comprising a BDO-based TPU (TPU-B1), as measured at 7-day intervals over 42 days. Composition viscosities were measured at 25 C. using a Brookfield LVT 4 viscometer; the viscosity results are reported in units of millipascal-seconds (mPa.Math.s).

[0115] FIG. 2: Bar chart showing the effect of storage temperature (25 C. and 4 C.) on the T peel performance of an ethyl cyanoacrylate composition (CEx1) comprising a BDO-based TPU (TPU-B1), as measured at 7-day intervals over 42 days. T-peel tests were performed in accordance with ASTM-710/ISO 11339. The T peel measurements are reported in newtons per millimeter (N/mm).

[0116] FIG. 3: Bar chart showing the effect of TPUs based on HQEE chain extender or BDO chain extender on the viscosity stability of curable cyanoacrylate compositions. Results are shown for Example Composition 2 (Ex2) and Example Composition 3 (Ex3), and Comparative Example Composition 2 (CEx2) and Comparative Example Composition 3 (CEx3). Room temperature (25 C.) viscosity measurements are reported in FIG. 3 using freshly prepared compositions tested immediately after formulation (T=0) and compositions that had been stored for 30 days at 25 C. immediately prior to testing (T=30DAYS). The TPU present in each composition is provided in FIG. 3 and whether said TPU is BDO-based or HQEE-based is specified.

[0117] FIG. 4: Bar chart showing the ratio of the viscosity of a tested composition at 30 days following storage at 25 C. (nominator; time calculated from the instant of formulation) to the initial viscosity (T=0, immediately after fresh preparing a composition; denominator) of said tested composition. Said ratio is hereinafter termed the 1-month ratio. All reported viscosities in FIG. 4 are as measured at 25 C. An unchanged viscosity measurement at T=0 and T=30 days would result in a 1-month ratio of unity (1.0). For convenient reference, a solid black line has been depicted in the bar chart to indicate the position of the 1-month ratio equal to unity. Bars with maximum values well below the solid black line show compositions exhibiting a decrease in viscosity over 30 days storage at room temperature, whereas, bars with maximum values very close to the solid black line show compositions exhibiting viscosity stability out to 30 days. Results are shown for Example Composition 1 (Ex1), Example Composition 2 (Ex2), and Example Composition 3 (Ex3), and for Comparative Example Compositions 4-10. The TPU present in each composition is provided in FIG. 4 and whether said TPU is BDO-based or HQEE-based is specified.

[0118] FIG. 5: Bar chart showing the T peel performance of Example Compositions (Ex1-3) and Comparative Example Compositions (CEx4-10) following 24 hour cure at 90 C. The TPU present in each composition is provided in FIG. 5 and whether said TPU is BDO-based or HQEE-based is specified.

[0119] FIG. 6: Bar chart showing the effect of TPUs based on HQEE chain extenders or BDO chain extenders on the T peel performance of cyanoacrylate compositions as a function of cure time. Results are shown for Example Composition 2 (Ex2), Example Composition 3 (Ex3), Comparative Example Composition 2 (CEx2), and Comparative Example Composition 3 (CEx3). Results for two curing conditions are depicted. The first curing condition tested was a 7 day cure at 25 C. The second curing condition tested, was a 3 day cure at 25 C., followed by a 1 day cure at 90 C. (termed an accelerated cure). The TPU present in each composition is provided in FIG. 6 and whether said TPU is BDO-based or HQEE-based is specified.

DETAILED DESCRIPTION

[0120] The present invention is directed to the use of a chain extender in the synthesis of TPUs that results in the TPU having a structural unit with the formula: OR.sup.1OArOR.sup.2O, wherein Ar is a C.sub.6-C.sub.20 aromatic group with at least one aromatic ring; R.sup.1 is C.sub.2-C.sub.10 alkyl group; and R.sup.2 is C.sub.2-C.sub.10 alkyl group wherein the TPUs bearing said structural unit are subsequently used as toughening agents in cyanoacrylate adhesives compositions. It has been surprisingly found that the use of said TPU toughening agent imparts to the resulting curable cyanoacrylate compositions long-term viscosity stability at room temperature (25 C.); i.e. for at least 1 month. By viscosity stability is meant that the viscosity does not drop from the starting viscosity after 1 month at room temperature.

[0121] TPUs are synthesised from polyols, isocyanate compounds and chain extender compounds. Therefore, it is to be understood that the chain extenders are components used in the synthesis of the TPU, and that the chain extenders become incorporated as a structural unit of the TPU. For the avoidance of doubt, there are no free, unreacted chain extenders present in the final toughened cyanoacrylate compositions of the present invention-rather, all chain extenders will have become structurally incorporated into the TPU toughening agent during synthesis of said TPU.

[0122] Owing to the stochastic nature of the polymerisation process, very slight variations can arise from batch to batch of TPU, even when identical components are mixed in an identical manner, at identical proportions. Accordingly, different batches of a TPU prepared using the same components, at identical weight percentages, can have a slightly different molecular weight (Mw)/Mw distribution.

Example TPUs

[0123] A range of TPU materials were synthesised and then formulated in curable cyanoacrylate compositions to test their suitability as toughening agents. All of the TPUs described in the following Example TPU Preparation sub-sections were prepared from a polyol, an isocyanate compound, and HQEE (Structure 1) chain extender. The curable cyanoacrylate compositions Example 1 (Ex1), Example 2 (Ex2), and Example 3 (Ex3) formulated with the Example TPUs of the following sub-sections, as identified in the Formulation Table (Table 1), are examples of curable cyanoacrylate compositions according to the present invention.

Preparation of Example TPUs: TPU-A1, TPU-A2, and TPU-A3

[0124] Three batches of an Example TPU-TPU-A1 (batch 1), TPU-A2 (batch 2), and TPU-A3 (batch 3)were prepared using identical components at identical weight percentages. Minor batch-to-batch variation in the Mw/Mw distribution of the resulting TPUs-TPU-A1, TPU-A2, and TPU-A3is reflected in the performance of the Example Compositions in which they are present (Ex1, Ex2, and Ex3, respectively), as shown for example in FIGS. 3-6. Said batches were each prepared as follows: A solid partially crystalline saturated co-polyester polyol, Dynacoll 7360 (359.71 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.17 g) ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (45.58 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. This is a quality control step relevant to the Mw distribution of the resulting TPU. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. HQEE (22.56 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0125] Components Used in the Preparation for Each of the TPU Batches TPU-A1, TPU-A2, and TPU-A3

TABLE-US-00001 Percentage Components Mass (g) by weight Dynacoll 7360 (polyol) 359.71 83.65% MDI 45.58 10.60% HQEE 22.56 5.25% Irganox 1010 2.17 0.5% Total 430.02 .sup.100%

Comparative Examples

[0126] A range of TPU materials were synthesised and then formulated in curable cyanoacrylate compositions to test their suitability as toughening agents. All of the TPUs described in the following Comparative Example TPU Preparation sub-sections were prepared from a polyol, an isocyanate compound, and a BDO chain extender (1,4-butanediol; Structure 2). CEx1, CEx2, CEx3, CEx4, CEx5, CEx6, CEx7, CEx8, CEx9, and CEx10, formulated with the Comparative Example TPUs of the following sub-sections, as identified in the Formulation Table (Table 1), are Comparative Examples of cyanoacrylate compositions; accordingly said Comparative Example cyanoacrylate compositions are compositions not according to the invention. Said compositions, comprising BDO-based TPUs have been characterised and they provide evidence of TPU-toughened cyanoacrylate compositions that do not exhibit long term (30 days) viscosity stability when stored at room temperature (25 C.), in contrast to compositions according to the present invention (FIG. 1, FIG. 3, and FIG. 4), emphasising the technical effect of employing TPUs as set out in the claims in curable cyanoacrylate compositions. The Comparative Examples of cyanoacrylate compositions were tested and shown to display good to excellent T peel performance when they had been stored at 4 C. prior to testing; however, all of these compositions displayed a decrease in viscosity over 30 days when stored at 25 C. (sometimes a dramatic >50% decrease in viscosity as compared to the initial viscosity), and this decrease in viscosity was matched by a corresponding decrease in T peel performance (for example, CEx1 performance in FIGS. 1 and 2). The decrease in viscosity referred to in connection with the Comparative Examples of curable cyanoacrylate compositions can be circumvented by replacing the BDO chain extender of the TPU component with a chain extender having the formula HOR.sup.1OArOR.sup.2OH, or with a chain extender that when structurally incorporated into said TPU component has the formula OR.sup.1OArOR.sup.2O, wherein Ar is a C.sub.6-C.sub.20 aromatic group with at least one aromatic ring; R.sup.1 is C.sub.2-C.sub.10 alkyl group; and R.sup.2 is C.sub.2-C.sub.10 alkyl group. A chain extender comprised by this formula is for example HQEE; in HQEE, Ar is a C.sub.6 aromatic group with an aromatic ring, and R.sup.1 and R.sup.2 are both C.sub.2 alkyl groups. HQEE is used as a chain extender for the TPUs that are present in the Example compositions. The use of TPUs based on for example, HQEE chain extender, for toughening of cyanoacrylate compositions is shown herein to impart significantly improved viscosity stability (relative to those comprising BDO-based TPUs; i.e. relative to the Comparative Examples), and is associated with T peel performance retention, when said compositions are tested following storage at room temperature (25 C.) for 30 days.

Preparation of Comparative Example TPU: TPU-B1 and TPU-B2

[0127] Two batches of a Comparative Example TPUTPU-B1 (batch 1) and TPU-B2 (batch 2)were prepared using identical components at identical weight percentages. Minor batch-to-batch variation in the Mw/Mw distribution of the resulting TPUs-TPU-B1 and TPU-B2is reflected in the performance of the Comparative Example Compositions in which they are present (CEx1 and CEx9, respectively). Said batches were each prepared as follows: A solid partially crystalline saturated co-polyester polyol, Dynacoll 7361 (344.64 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g) ex Ciba. A 1-3 mbar vacuum was then applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (45.2 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (5.37 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0128] Components Used in the Preparation for Each of the TPU Batches TPU-B1 and TPU-B2

TABLE-US-00002 Percentage Components Mass (g) by weight Dynacoll 7361 (polyol) 344.64 86.77 MDI 45.2 11.38 Butanediol 5.37 1.35 Irganox 1010 2.0 0.5 Total 397.21 100

Preparation of Comparative Example TPUs: TPU-C1 and TPU-C2

[0129] Two batches of a Comparative Example TPUTPU-C1 (batch 1) and TPU-C2 (batch 2)were prepared using identical components at identical weight percentages. Minor batch-to-batch variation in the Mw/Mw distribution of the resulting TPUs-TPU-C1 and TPU-C2is reflected in the performance of the Comparative Example Compositions in which they are present (CEx2 and CEx3, respectively), as shown for example in FIGS. 3 and 6. Said batches were each prepared as follows: A solid partially crystalline saturated co-polyester polyol, Dynacoll 7360 (370.36 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.15 g) ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (46.93 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum for (1-3 mbar) 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol chain extender (BDO; Structure 2) (10.56 g) was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0130] Components Used in the Preparation for Each of the TPU Batches TPU-C1 and TPU-C2

TABLE-US-00003 Percentage Components Mass (g) by weight Dynacoll 7360(polyol) 370.36 86.13% MDI 46.93 10.91% BDO 10.56 2.46% Irganox 1010 2.15 0.50% Total 430.0 100%

Preparation of Comparative Example TPU: TPU-D

[0131] A solid highly crystalline saturated co-polyester polyol, CAPA 2201 (303.88 g) ex Perstorp, was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g) ex Ciba. A 1-3 mbar vacuum was applied. The polyol is described as having a melting point (m.p.) of 70 C. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (77.16 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO (isocyante groups) at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (16.64 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0132] Components Used in the Preparation of TPU-D

TABLE-US-00004 Percentage Components Mass (g) by weight CAPA 2201 (polyol) 303.88 76.03 MDI 77.16 19.31 Butanediol 16.64 4.16 Irganox 1010 2.0 0.5 Total 399.68 100

Preparation of Comparative Example TPU: TPU-E

[0133] A polyether glycol polyol, Terathane 2000 (305.2 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g) ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (76.4 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (16.48 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0134] Components Used in the Preparation of TPU-E

TABLE-US-00005 Percentage Components Mass (g) by weight Terathane 2000 (polyol) 305.2 76.3 MDI 76.4 19.1 Butanediol 16.48 4.12 Irganox 1010 2.0 0.48 Total 400.08 100

Preparation of Comparative Example TPU: TPU-F

[0135] A solid highly crystalline saturated co-polyester polyol, Dynacoll 7390 (342.04 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g) ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (47.2 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (10.16 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0136] Components Used in the Preparation of TPU-F

TABLE-US-00006 Percentage Components Mass (g) by weight Dynacoll 7390 (polyol) 342.04 85.21 MDI 47.2 11.76 Butanediol 10.16 2.53 Irganox 1010 2.0 0.5 Total 401.40 100

Preparation of Comparative Example TPU: TPU-G

[0137] A solid partially crystalline saturated co-polyester polyol, Dynacoll 7363 (353.12 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g) ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (35.6 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (7.68 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0138] Components Used in the Preparation of TPU-G

TABLE-US-00007 Percentage Components Mass (g) by weight Dynacoll 7363 (polyol) 353.12 88.63 MDI 35.6 8.94 Butanediol 7.68 1.93 Irganox 1010 2.0 0.5 Total 398.4 100

Preparation of Comparative Example TPU: TPU-H

[0139] A solid partially crystalline saturated co-polyester polyol, Dynacoll 7363 (344.88 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g), ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (46.0 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (9.64 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0140] Components Used in the Preparation of TPU-H

TABLE-US-00008 Percentage Components Mass (g) by weight Dynacoll 7363 (polyol) 344.88 86.09 MDI 46.0 11.48 Butanediol 9.64 2.41 Irganox 1010 2.0 0.5 Total 402.52 100

Preparation of Comparative Example TPU: TPU-J

[0141] A solid partially crystalline saturated co-polyester polyol, Dynacoll 7360 (344.88 g), was melted at temperatures between of 110-120 C. in a three necked resin kettle along with Irganox 1010 antioxidant (2.0 g) ex Ciba. A 1-3 mbar vacuum was applied. Melting whilst under vacuum increases the efficiency of the degassing and moisture removal procedure whilst reducing the possibility of polyol depletion due to deposition on the vessel side walls. Once melted (30-40 mins) the polyol was stirred for 30 mins at 100 rpm under vacuum, this allows for further removal of unwanted moisture. The vacuum was removed by the introduction of a slight N.sub.2 flow. Methylene bis-phenyldiisocyanate (MDI) flake (44.0 g) was added through a wide necked funnel. The vessel was stoppered and the N.sub.2 bleed removed. The reaction was maintained at 115 C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction was again placed under vacuum (1-3 mbar), for 15 mins. The vacuum was removed and three 1 g samples were taken at this time. These samples were taken in order to correctly determine the amount of unreacted NCO at this time. The reaction vessel was stoppered and again placed under vacuum with continuous stirring. The vacuum was removed by the introduction of a slight N.sub.2 flow. Butanediol (8.2 g) chain extender was added via a dropping funnel ensuring full delivery under N.sub.2. The vessel was again stoppered and the mixing speed was maintained at 250 rpm. The reaction was allowed to proceed at a temperature of 115 C. ensuring that the exothermic reaction did not exceed 125 C. After addition of the chain extender the reaction proceeded for 15 mins without vacuum and 15 mins with vacuum.

[0142] Components Used in the Preparation of TPU-J

TABLE-US-00009 Percentage Components Mass (g) by weight Dynacoll 7360 (polyol) 344.64 86.77 MDI 45.2 11.38 Butanediol 5.37 1.35 Irganox 1010 2.0 0.5 Total 397.21 100

TABLE-US-00010 TABLE 1 Formulation Table Example Compositions Comparative Example Compositions Components Ex1 Ex2 Ex3 CEx1 CEx2 CEx3 CEx4 CEx5 CEx6 CEx7 CEx8 CEx9 CEx10 TPU-A1 10.0 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A wt % TPU-A2 N/A 10.0 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A wt % TPU-A3 N/A N/A 10.0 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A wt % TPU-B1 N/A N/A N/A 10.0 N/A N/A N/A N/A N/A N/A N/A N/A N/A wt % TPU-B2 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 10.0 N/A wt % TPU-C1 N/A N/A N/A N/A 10.0 N/A N/A N/A N/A N/A N/A N/A N/A wt % TPU-C2 N/A N/A N/A N/A N/A 10.0 N/A N/A N/A N/A N/A N/A N/A wt % TPU-D N/A N/A N/A N/A N/A N/A 10.0 N/A N/A N/A N/A N/A N/A wt % TPU-E N/A N/A N/A N/A N/A N/A N/A 10.0 N/A N/A N/A N/A N/A wt % TPU-F N/A N/A N/A N/A N/A N/A N/A N/A 10.0 N/A N/A N/A N/A wt % TPU-G N/A N/A N/A N/A N/A N/A N/A N/A N/A 10.0 N/A N/A N/A wt % TPU-H N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 10.0 N/A N/A wt % TPU-J N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 10.0 wt % Ethyl 89.495 wt %; in each case Cyanoacrylate Boron 0.005 wt % trifluoride That is: a final concentration of (BF.sub.3; stabiliser) 50 ppm BF.sub.3, in each case INHANCE 0.50 wt %, in each case microparticles: UH-1250

Formulation of Compositions

[0143] Formulation details relating to the Example Compositions and the Comparative Example Compositions reported in Table 1 are described in this sub-section.

[0144] All compositions reported in Table 1 were formulated to comprise a total of 89.495 wt % curable ethyl cyanoacrylate, 0.005 wt % of the stabiliser BF.sub.3 (that is, 50 ppm by weight), and then 10 wt % of a particular TPU and 0.5 wt % of surface modified microparticles of ultra-high molecular weight polyethylene (UH-1250 INHANCE microparticles, in this case) wherein the weight-percentages (wt %) are based on the total weight of the composition. During formulation of the Example/Comparative Example Compositions said microparticles were added at the same time as the particular TPU component; however, it is to be understood that surface modified microparticles of ultra-high molecular weight polyethylene are an optional component for compositions according to the present invention. Stabiliser Solution (1000 ppm BF.sub.3 in ECA) was used to adjust the amount of BF.sub.3 stabiliser in the curable ethyl cyanoacrylate component to the desired concentration of 50 ppm (forming a stabilised ECA component); then, the particular TPU was finely sliced and rapidly mixed with the stabilised ECA component at a temperature of 65 C. for a time sufficient dissolve the TPU component into the stabilised ECA component. Surface modified microparticles of ultra-high molecular weight polyethylene (such as for example, UH-1250 INHANCE microparticles) were added at the same time as the finely sliced TPU, at a temperature of 65 C. and rapidly mixed for a time sufficient dissolve the microparticles. Upon cooling to room temperature (25 C.), formulation of the given composition was complete. Completion of formulation was taken to be T=0; thus, samples were taken at this time for tests (per results shown in FIGS. 1-4). The samples of each given composition were then stored, either at room temperature (25 C.) or at 4 C., and subjected to various tests as described in the Results of Tests on Compositions section.

[0145] Freshly prepared stock Stabiliser Solution is used to mix in a stabiliser of the curable cyanoacrylate component (such as BF.sub.3) to a pure ECA component of the compositions (forming thereby a stabilised ECA component), prior to the addition of the given TPU, to ensure that the desired final concentration of stabiliser can be conveniently achieved (for example, 50 ppm BF3, or for example, 20 ppm BF3). Stabiliser Solution comprises curable ethyl cyanoacrylate (ECA); therefore the total amount of curable ethyl cyanoacrylate (ECA) reported for the compositions described in Table 1 includes the contribution from both the pure ECA solution and the Stabiliser Solution. By way of example, the composition Example 1 (Ex1) comprises a stabiliser, BF.sub.3, at a final concentration of 50 ppm by weight, said BF.sub.3 content being adjusted/determined by the addition of Stabiliser Solution; accordingly Example Composition 1 (Ex1) comprises a total of 89.495 wt % ECA (ECA from the initially pure ECA solution and yet further ECA from the stock Stabiliser Solution comprising 1000 ppm BF.sub.3), wherein the wt %'s are based on the total weight of the composition.

[0146] Results of Tests on Compositions

Initial tests to identify toughening agents for cyanoacrylate compositions focused on TPUs based on BDO chain extenders; see Comparative Examples 1, 2 and 3, CEx1-3, as identified in the Formulation Table (Table 1). However, as can be seen from FIG. 1 and FIG. 3, testing revealed that when such compositions comprising BDO-based TPU (TPU-B1) had been stored at room temperature (25 C.)which it is envisioned would be the most convenient storage temperature for end-use applicationsthe viscosity of such cyanoacrylate compositions decreases from the initial viscosity at day 0 (T=0), as measured at 7-day intervals over 42 days. Indeed, for the composition Comparative Example 1 (CEx1), comprising TPU-B1, as shown in FIG. 1, the viscosity was found to have decreased strikingly by >50% of the starting viscosity within 28 days, with yet further decreases in viscosity recorded out to 42 days. Without wishing to be bound by any theorem, it is inferred that this behaviour seen in cyanoacrylate compositions following storage at room temperature (25 C.) may be attributable to the continual breakdown of hydrogen bonding within the BDO-based TPU component over time. Viscosities were measured using a Brookfield LVT 4 viscometer. The striking decrease in viscosity over time seen for the composition (CEx1) comprising BDO-based TPU (TPU-B1) shown in FIG. 1, was demonstrated to be further associated with a simultaneous decrease in T peel performance (FIG. 2).

[0147] As can be seen in FIG. 2, a drop in T-peel performance was measured on samples of a Comparative Example composition (CEx1) when tested every 7-days over 42 days (i.e. >1 month), during which time the curable cyanoacrylate composition comprising a BDO-based TPU (TPU-B1) was stored at 25 C. The results reported in FIG. 2 were obtained following 24 hour cure at 90 C. T-peel tests were performed in accordance with ASTM-710/ISO 11339. Storage at 4 C. prior to testing did not appear to result in long-term decline in T peel performance (FIG. 2).

[0148] However, it was surprisingly found that replacement of BDO (Structure 2), with HQEE (Structure 1) as the chain extender component of the TPU that is used to toughen the cyanoacrylate composition resulted in cyanoacrylate compositions exhibiting viscosity stability following 30 days storage at room temperature (25 C.). Viscosity stability refers to a substantially unchanged viscosity at the start and end of the measuring time period. FIG. 3 shows the results of viscosity measurements recorded at 25 C., following 30 days storage at room temperature (25 C.), on Example Composition 2 (Ex2) and Example Composition 3 (Ex3) both of which comprise an HQEE-based TPU (TPU-A2 and TPU-A3, respectively), and Comparative Example Composition 2 (CEx2) and Comparative Example Composition 3 (CEx3), both of which Comparative Examples comprise a BDO-based TPU (TPU-C1 and TPU-C2, respectively). As is clear from FIG. 3, although the compositions comprising a BDO-based TPU (CEx2, CEx3) exhibit a decrease in viscosity over the 30 day test-period as compared to the initially recorded viscosity at T=0, both of the Example compositions comprising an HQEE-based TPU (Ex2, Ex3) exhibit viscosity stability. Following on from the test results reported in FIG. 3, a range of further cyanoacrylate compositions comprising BDO-based TPUs were prepared (CEx4-CEx10; see Table 1) and they were compared in tests for viscosity stability versus Example Compositions comprising HQEE-based TPUs (Ex1-Ex3; see Table 1), by recording a 1-month ratio value for each composition (FIG. 4). A 1-month ratio refers to the ratio of the viscosity as measured following storage at room-temperature for 30 days after formulation (25 C. storage; T=30 days) to the initial viscosity (T=0; measured at 25 C. using freshly formulated compositions). The results are summarised in Table 2.

TABLE-US-00011 TABLE 2 1-Month ratio table Chain extender Viscosity The ratio of the on which the (mPa .Math. s; viscosity at T = TPU present in Viscosity 25 C.) 30 days to the the com- (mPa .Math. s; at T = 30 initial viscosity at Compo- position 25 C) at days storage at T = 0 (1-Month sition is based T = 0 25 C. ratio) CEx4 BDO 42.5 29.0 0.68 CEx5 BDO 293 133 0.45 CEx6 BDO 175 123 0.70 CEx7 BDO 103 77.1 0.74 CEx8 BDO 103 89.2 0.86 CEx9 BDO 171 94.8 0.55 CEx10 BDO 101 55.5 0.55 Ex1 HQEE 112 110 0.98 Ex2 HQEE 70.7 73.8 1.04 Ex3 HQEE 79.7 82.1 1.03

[0149] Strikingly, only the compositions comprising an HQEE-based TPU (Ex1, Ex2, Ex3), exhibit long-term viscosity stability; that is, a 1-Month ratio within 5% of unity. These results are graphically summarised in FIG. 4.

[0150] In addition to BDO, chain extenders such as 1,3-propanediol, 1,8-octanediol, and 1,12-dodecanediol were tested as replacement chain extenders in the synthesis of TPUs, which TPUs were subsequently tested as toughening agents in cyanoacrylate compositions. However, none of the TPUs synthesised with said chain extenders, when formulated with cyanoacrylate, resulted in toughened cyanoacrylate compositions characterised by long-term (30 days) viscosity stability at room temperature. Rather, in each such case, the viscosity steadily declined over time, with a corresponding decrease in T peel strength (N/mm) as compared to the initial T peel strength at T=0. Thus, these findings of poor long term viscosity performance, and the Results for the Comparative Example Compositions comprising BDO-based TPUs (as shown in FIGS. 3 and 4), emphasise the striking technical effect-viscosity stabilisation-achieved by using HQEE as a chain extender in a TPU that is subsequently formulated into a cyanoacrylate composition. Example Compositions equivalent to those reported in Table 1 were prepared lacking any INHANCE microparticles (the mass of the microparticles being replaced by a further 0.50 wt % ethyl cyanoacrylate); it was found that the removal of this optional component had no detrimental effect on the 1-month ratio values of the equivalent Example Compositions. Similarly, replacement of the optional UH-1250 INHANCE microparticles component with UH-1080 INHANCE microparticles at 0.50 wt % had no detrimental effect on the 1-month ratio values of the equivalent compositions.

[0151] As seen in FIG. 5, the Example Compositions exhibit strong T peel performance following 24 hour cure at 90 C., on the order of 6 N/mm to 10 N/mm, which is well within the margins of the minimum and maximum values seen for the Comparative Example Compositions. Thus, formulation of cyanoacrylate compositions with HQEE-based TPUs does not adversely impact the T peel performance of the compositions. Further characterisation of Example Compositions Ex2 and Ex3 and Comparative Example Compositions CEx2 and CEx3, revealed a remarkably enhanced T peel performance relative to 7 days cure at room temperature (25 C.), when said compositions are subjected to accelerated cure. Said accelerated cure consists of curing 3 days at 25 C. followed by 1 day at 90 C. (FIG. 6). T peel tests were performed in accordance with ASTM-710/ISO 11339. The enhancement of T peel performance seen in FIG. 6 is suggestive, and indicates that in addition to possessing strong initial bonding strength, the strength of bonding is likely to increase over time, which is a desirable property; for example in adhesives applications. Thus, the Example Compositions, and compositions according to the present invention, are cyanoacrylate compositions that exhibit long term viscosity stability at room temperature, and that exhibit strong T peel performance when cured.

[0152] The words comprises/comprising and the words having/including when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0153] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.